I generally like Decathlon, never had any disappointments with anything I've bought from there. But I'm not the runner. There are some reviews criticising the quality of the running shirts. Dh had a shirt (not from Decathlon) which chaffed him under the arms, and he ended up with a nasty fungal infection a result, so I'm not taking any chances.
I’ve had a Nike vest that chafed under my arms - I think that’s more to do with the fit rather than quality in that case.
I’ve only ever placed one order with decathlon - didn’t like it enough to go back. Flimsy. Not v well fitting IIRC. Good for a newbie who doesn’t want to spend much before they know what they like, but not investment pieces.
I like it. You probably need to go and have a look irl though. I find the sizing comes up small and some of the running leggings are a bit thin. Most of my favourite running items are from there though.
Dh never wears compression gear. He prefers loose kit.
The chaffing he had was not from an ill-fitting garment, but from the movement of his arms against his ribs. (Much as I love him and respect his achievements, the man runs like a newly-hatched stork on the flat! It's only on gradients that he looks like his limbs belong to him. )
Auntie they have a strange business model thet catches a lot of people out. So I don't like to recommend them. Basically you sign up to be a member and then they charge you£44 port month for a new outfit unless you do the month, it's a monthly payment that is hard to cancel.